A paper showing a strong genetic contribution to social responsibility was published in the December 22 issue of Proceedings of the Royal Society: Biological Sciences, 271, 2583-2585, entitled “Genetic and environmental contributions to pro-social attitudes: a twin study of social responsibility.” The study compared identical twins with non-identical twins to see how much they agreed on 22 questions, such as “I am a person people can count on,” “It is important to finish anything you have started,” and “Cheating on income tax is as bad as stealing,” using a scale from 1 (strongly disagree) to 5 (strongly agree). Answers are known to predict real-life behavior such as whether a person votes in elections or volunteers to help others.
The twins came from the University of London Twin Register. There were 174 pairs of monozygotic (identical twins, who share all their genes) and 148 pairs of dizygotic (non-identical twins, who share only half their genes). If monozygotic twins agree more than dizygotic twins it suggests that that morality has a biological basis and is part of our evolved psychology.
The answers of the identical twins were almost twice as alike as those of the non-identical twins. The results showed that genes account for 42% of the individual differences in attitudes, growing up in the same home for 23%, and differences within the same home for the rest.
The study also found that genes had a stronger influence on males than females (50% vs. 40%) and that home upbringing had a stronger influence on females (40% vs. 0%). This suggests parents may watch over the behavior of daughters more carefully than they do for their sons.
In previous research Rushton has shown that genes influence people’s levels of altruism and aggression–including feelings of empathy like enjoying watching people open presents and acts of violence such as fighting with a weapon. Rushton has also demonstrated that the male sex hormone testosterone sets the levels of aggression and altruism.
When asked about his findings Prof. Rushton noted, “They join a host of recent research in showing that both genes and upbringing influence almost every human behavior. It is especially interesting to see that this applies to moral attitudes.” He said that he agreed with George Eliot’s sentiment: “What do we live for, if it is not to make life less difficult for each other?”